1. Field of the Invention
The present invention relates to an image sensing apparatus, imaging system, and image sensing apparatus driving method.
2. Description of the Related Art
Previously proposed conventional image sensing apparatus has a pixel array including an optical black region and effective pixel region (see Japanese Patent Laid-Open No. 2001-45383). According to the technique disclosed in Japanese Patent Laid-Open No. 2001-45383, a shift register for scanning the respective rows or columns of the pixel array is formed from a plurality of circuit blocks. A decoder circuit for selecting one of the circuit blocks is arranged on the input side of the shift register. By selecting a circuit block by the decoder circuit, scanning of pixels can start for each pixel block including a plurality of pixels in an effective pixel region.
Recently, image sensing apparatuses such as a video camera and still camera require a high-precision electronic anti-shake (camera shake correction) function. As a technique for implementing the electronic anti-shake function, the present inventor has examined to shift a readout region, which is a partial region of the effective pixel region, in the direction of camera shake in the effective pixel region. To shift the readout region in the effective pixel region in order to implement the electronic anti-shake function, the readout start position of the readout region is changed for each pixel (for each row and each column) in the effective pixel region.
According to the technique in Japanese Patent Laid-Open No. 2001-45383, when the readout start position does not exist at the end of a pixel block, pixels are sequentially skipped from a pixel at the end of a predetermined pixel block to that at the readout start position after the end of scanning the optical black region. This may prolong the period until scanning of the readout region starts for each pixel in the effective pixel region after the end of scanning the optical black region.
If a decoder circuit for selecting one of flip-flops which build the shift register is arranged on the input side of the shift register in order to scan the pixel array, the readout start position of the readout region can be changed for each pixel in the effective pixel region. In this case, however, the size of a circuit for scanning the pixel array may become large, complicating the arrangement of the image sensing apparatus.